Apparatus to determine tension in a flexible strand

ABSTRACT

A TENSIOMETER APPARATUS THAT MEASURES STRAND TENSION OF A BELT, ROPE, WIRE, CABLE OR THE LIKE, UTILIZING A METHOD OF TORQUEING AND DEFLECTING A SEGMENT OF THE STRAND TO A STRAND REFERENCE ANGLE.

P 23, 1971 o. L. KESSLER 3,608,371

APPARATUS TO DETERMINE TENSION IN A FLEXIBLE STRAND Filed Bay 28, 1968 2 Sheets-Sheet 1 INVIZNTOR. DAVID L. KESSLER ATTORNEY D. KESSLER 3,608,371

APPARATUS TO DETERMINE TENSION IN A FLEXIBLE STRAND Sept. 28, 1971 2 Sheets-Sheet 2 Filed llay 28, 1968 INVENTOR. DAVID L. KE

SSLER ATTORNEY United States Patent Office 3,608,371 Patented Sept. 28, 1971 3,608,371 APPARATUS TO DETERMINE TENSION IN A FLEXIBLE STRAND David L. Kessler, Denver, Colo., assiguor to The Gates Rubber Company, Denver, Colo. Filed May 28, 1968, Ser. No. 732,595 Int. Cl. G011 5/06 US. Cl. 73-144 6 Claims ABSTRACT OF THE DISCLOSURE e A tensiometer apparatus that measures strand tension of a belt, rope, wire, cable or the like, utilizing a method of torqueing and deflecting a segment of the strand to a standard reference angle.

This invention relates to a method and an apparatus for determining tension in a strand of belt, rope, wire, cable or the like wherein the functioning of the apparatus is dependent upon deflecting the strand to an angle.

The functional integrity of many apparatus is dependent on strand tension. For example, wire strands used as reinforcement for hose must be applied to the hose during the manufacturing process while the wire strands are under tension. In V-belt drive systems, the tension of the V-belt strand is important to insure maximum bearing life, maximum V-belt and sheave life, and of more importance, to insure that rated torque is being transmitted by the V-belt strand. Typically, strand tension is determined by deflecting the strand. Some strand tensiometers apply a constant normal force to the strand between two reference points and then establish strand tension by how far away the strand is deflected from the two reference points. Other tensiometers deflect the strand a standard amount away from two reference points and then establish strand tension by the normal force required to deflect the strand. Some problems are associated with the aforementioned tensiometers. One problem is the complication of attaching the tensiometer to a strand so a force may be applied to a segment of strand. Another problem with some tensiometers is the error which may be introduced when a span of strand, rather than a segment thereof, is deflected.

Included among the objects of this invention is the establishment of a method to determine strand tension by applying a torque to a segment of strand and deflecting the strand to an angle.

Another object of this invention is to provide a simple portable tensiometer apparatus having suitable accuracy and which apparatus is easy and fast to use.

Still another included object of this invention is to provide a tensiometer apparatus which is self-adjusting to various strand cross-sections and which has a scale retention means.

Part of this invention relates to a method of determining strand tension by applying a torque to a segment of strand and deflecting the strand to a standard angle. Application of the method results in a tensiometer apparatus that is simple, accurate and easy to use.

In a simple, preferred form, the tensiometer apparatus has only one moving part-a cantilever leaf spring mounted to a body. The body has two projecting tangs for engaging and applying torque to a strand segment being tested for tension. In a more sophisticated form, this invention includes a means for adjusting for various strand cross-sections, and a means for retaining a scale tension reading. The scope of this invention is best understood in conjunction with the appended drawings and description thereof.

FIG. 1 is a force diagram showing a segment of flexible strand being angularly deflected to illustrate the method of determining tension in the strand.

FIG. 2 shows a tensiometer apparatus being positioned on a V-belt strand of a V-belt drive system.

FIG. 3 is a view similar to that of FIG. 2 but showing an enlarged view of the tensiometer apparatus and a segment of V-belt strand.

FIG. 4 is a view similar to that of FIG. 3 showing the segment of V-belt strand being deflected with the tensiometer apparatus to determine strand tension.

FIG. 5 shows a variation of the tensiometer apparatus wherein a tension spring is used.

FIG. 6 shows a variation of the tensiometer apparatus wherein a coil spring is used.

FIG. 7 shows a variation of the tensiometer apparatus wherein a compression spring is used.

FIG. 8 shows a tensiometer apparatus having an automatic adjustment means which compensates for variations in strand thickness.

FIG. 9 shows a variation of the tensiometer apparatus illustrated by FIG. 8.

FIG. 10 shows a tensiometer apparatus having a scale retention means.

The method of determining the tension in a flexible strand by applying a torque to a segment of the flexible strand is explained with reference to FIG. 1. An external torque is applied to a segment of flexible strand 1 by a first member 2 and a second member 3. The torque applied is represented by the equal forces F acting a distance S apart. The applied torque deflects the flexible strand through an angle A. The segment of flexible strand 1 resists the applied torque as a function of the tension in the flexible strand. The tension T in the flexible strand is the sum of the initial tension plus any tension which might be induced by the applied torque. The ap plied torque taken about first member 2 is the product of the force F and the distance S. The torque which counteracts the applied torque is the product of a sine component of the tension T and the distance S. The torque relationship may be expressed by the following equation for a perfectly flexible strand.

F(S)=T sin A(S) or in a more simplified form,

F :T sin A If the angle A or its complementary angle B is held constant, then sin A will also be a constant and the force F becomes directly proportional to the tension. Accordingly, the tension in a flexible strand may be directly determined by the method of calibrating a force required while torqueing a segment of flexible strand to a standard angle.

The operation and advantages of the above method may best be understood in conjunction with a tensiometer apparatus as applied to a V-belt drive system. Referring to FIGS. 2 and 3, a preferred embodiment of this invention is shown being positioned on a V-belt strand 5. The tensiometer 6 has a body 7 from which projects two tangs. A first tang 8 is positioned against the inner surface 9 of the V-belt strand 5 while a second tang 10 is positioned against the outer surface 11 of the V-belt strand 5. A cantilever type spring 12 has one end 13 securely fastened to the body 7 which allows the free end 14 of the spring 12 to be deflected with respect to the body 7. The spring 12 need have no special cross-section or be of any particular material. The spring 12 must have a repeating resiliency so it can be used to calibrate the force required to deflect the V-belt strand 5. A preferred embodiment of this invention utilizes commercially available flat clock springs for the spring 12.

After the tensiometer 6 has been positioned on the V- belt strand as illustrated by FIGS. 2 and 3, a clockwise force P as indicated by the arrow is applied to the free end 14 of the spring 12 as shown in FIG. 4. Application of the force P reacts over the length of the spring 12 and causes the body 7 to rotate in a clockwise manner which results in the first tang 8 moving upwardly and the second tang 10 moving downwardly. The tangs induce a clockwise torque to deflect the V-belt strand 5 by application of the-forces F acting apart at a distance S. The force P acting over the length of the spring 12 is proportional to a force F acting at the distance S. Application of the force P is continued until the body 7 is rotated to the point that a reference means on the body 7 just comes in contact or alignment with the outer surface 11 of the V-belt 5; Alignment of the outer surface 11 with the reference means 15 signifies the establishment of a stand ard' complementary angle B. The reference means 15 may be of any convenient form such as a line, a point, a gravure, a set of electrical contacts, et cetera. A preferred embodiment of this invention has a tang as the reference means The relative position of the spring 12 with respect to the body 7 is read from a calibrating scale 16 located on the body 7 when proper alignment has been achieved between the reference means 15 and outer surface 11. The calibrating scale 16 may be unitized to give direct readings in belt tension or any other convenient unit from which belt tension can be determined. The calibrating scale 16 is substantially linear in nature except for the first portion 17 of the scale 16. The non-linearity is due to the flexural rigidity of the V-belt 5.

A tensiometer apparatus having a cantilever type leaf spring to calibrate the application of a force was proffered in FIGS. 2, 3, and 4. However, the scope of this invention is not to be limited by any particular type of spring biasing means. Referring to FIG. 5, a movable arm 20 has one end 21 pivotally attached to the body 7. A tension type spring having its first end 22 attached to the body 7 and its second end 23 attached to the movable army 20 is used to calibrate the force P required to deflect a V-belt strand. The operation of such a tensiometer is the same as that previously explained.

The tensiometer apparatus depicted by FIGS. 6 and 7 are similar to that apparatus of FIG. 5. A coil type spring 24 is used to calibrate the force P in the apparatus of FIG. 6 whereas a compression type spring 25 is used vto calibrate the force P in the apparatus of FIG. 7. The functional operation of the tensiometer apparatus is the same as that previously explained.

Economical tensiometer apparatus that gives sufficiently accurate strand tension for a given strand thickness was heretofore described. Referring to FIG. 4, it readily determinable that as the thickness 18 of the V-belt strand 5 becomes smaller, the complementary angle B becomes larger which results in the V-belt strand 5 being deflected to a lesser extent. Deflecting the belt 5 to a lesser extent decreases the accuracy of the tensiometer apparatus and requires a different unitization of the calibrating scale 16. Another preferred embodiment of this invention is a tensiometer apparatus that adjusts to strands having different thickness. For ease of explanation, a tensiometer apparatus being used in a fashion similar to that of FIG. 4 is depicted by FIG. 8. The tensiometer 30, has a body 7, from which projects a first tang 8 and a second tang 10 which tangs are used to induce a clockwise torque to the V-belt strand. Loosely and pivotally attached about the second tang 10 is a beam 31. A spring means 32 having one end attached to the body 7 and the other end attached to the beam 31 applies a bias force that tends to rotate the beam 31 in a counter-clockwise manner. The first end 33 of the beam 31 is forced in contact with the outer surface 11 of the V-belt strand 5. The center portion 34 of the beam 31 is forced in contact with the V- belt strand 5 by the second tang 10 when the clockwise force P is applied. The second end 35 of the beam 31 is the reference means similar to the reference means 15 of FIG. 4. The first end 33, the center portion 34 and the second end 35 establish the complementary angle B which is constant for strands of different thicknesses. Additional calibrating scales 36 located on the body 7 permit the direct read out of strand tension for strands having different fiexural rigidity.

The tensiometer apparatus of FIG. 8 establishes a constant complementary angle B with reference to the outer surface 11 of the V-belt strand 5. Sometimes the outer surface of the V-belt strand may be rough because of wear which may cause an erroneous establishment of the complementary angle B. The scope of this invention also encompasses tensiometer apparatus that utilizes the inner surface of a strand to establish the complementary angleB. For example, the inner surface of a V-belt strand oftentimes is smooth and continuous when the outer surface of the same V-belt strand is rough and irregular.

Referring to FIG. 9, a tensiometer apparatus 37 is also shown which is similar in scope and usage to the apparatus of FIG. 8. The apparatus of FIG. 9 uses the inner surface of the V-belt strand 5 to establish the complementary angle B. The tensiometer apparatus 37 is thesame as the tensiometer apparatus 30 except the beam 31 is loosely and pivotally attached about the first tang 8 rather than the second tang 10. A spring means 32 having one end attached to the body 7 and the other end attached to the beam 31 applies a bias force that tends to rotate the beam in a counter-clockwise manner. The first end 33 of the beam 31 is forced in contact with the inner surface 9 of the V-belt strand 5. The center portion 34 of the beam 31 is forced in contact with the V-belt strand 5 by the first tang 8 when the clockwise force '1 is applied. The second end 35 of the beam 31 is the reference means which is aligned with the inner surface 9 of the V-belt strand 5 in a fashion similar to that described for the reference means 15 of FIG. 4. The first end 33, the center portion 34 and the second end 35 establishes the complementary angle B along the inner surface 9 of the V-belt strand 5. The complementary angle B is constant for strands of different thicknesses. Additional calibrating scales 36 permit the direct read out of strand tension for strands having different flexural rigidity.

Referring to FIG. 10, a scale retention read out device is illustrated on the reverse side of the body 7. The read out device may be incorporated on each of the heretofore described embodiments of this invention. The scale retention device comprises an arm 38 which has one end 39 pivotally attached to the body 7. The free end of the arm 38 has an engageable lip 40 which is engaged by the spring 12 when the end 14 is displaced in a now counter-clockwise manner. Engagement of the lip 40 causes the arm to rotate in a counter-clockwise manner with the spring 12. The lip 40 does not engage the spring 12 when the spring 12 is rotated in a clockwise manner. A sufficient amount of fric tion is maintained at the pivotally attached end 39 to keep the arm in any given position after it has been displaced by the movement of the spring 12. Accordingly, the arm 38 serves to retain the deflected position of the spring 12. The relative position of the arm 38 is read from the appropriate scale to calibrate the force P.

I claim:

1. An apparatus to determine a tensional force being carried by a flexible strand, which comprises:

a body;

at least a first and second strand-engaging tang that protrude outwardly and away from said body; and said first and second tang each having a strand-engaging surface;

a cantilevered spring having its supported end attached to said body in such a manner that the plane of defiection of the unsupported end of the said cantilevered spring is substantially perpendicular to the strand-engaging surface of said first and second tangs;

a calibrating scale means on at least one side of said body to establish the relative position between said body and the unsupported end of said cantilevered spring when the unsupported end is deflected; and

a reference means positioned on said body to establish a predetermined angular relationship between the strand-engaging surface of said first strand-engaging tang, the strand-engaging surface of said second strand-engaging tang, and said reference means, said reference means coacting with a surface of the strand to indicate when the segment of strand between said tangs has been deflected a predetermined amount corresponding to said predetermined angular relationship.

of said beam, the strand-engaging surface near the pivotal axis of said beam, and said reference means;

a cantilevered spring having its supported end attached to said body in such a manner that the plane of deflection of the unsupported end of said cantilevered spring is substantially perpendicular to the strandengaging surface of said first tang and the strandengaging surface near the pivotal axis of said beam; and

a calibrating scale means on at least one side of said body to establish the relative position betwen said body and the unsupported end of said cantilevered spring when the unsupported end is deflected.

5. An apparatus according to claim 4 having a scale retention readout device which comprises:

an arm having its first end pivotally attached to said body such that the plane of rotation of said arm is 2. An apparatus according to claim 1 having a scale retention read out device, which comprises:

an arm having a first end pivotally attached to said substantially parallel to the plane of deflection of said spring; and

an engageable lip that protrudes from the second end of said arm to engage said spring and rotate said arm in a unidirectional manner when the unsupported end of said spring is deflected.

6. An apparatus to determine a tensional force being carried by a flexible strand, which comprises:

a body;

a first strand-engaging tang that protrudes outwardly and away from said body and said tang having a strand-engaging surface;

a beam pivotally attached to said body, said beam having a strand-engaging surface near its first end and said beam having a strand-engaging surface near the pivotal axis of said beam;

a biasing means between said body and said beam to bias the strand-engaging surface near the first end of said beam toward the strand-engaging surface of said first strand-engaging tang;

a reference means on the second end of said beam to establish a predetermined angular relationship between the strand-engaging surface near the first end of said beam, the strand-engaging surface near the pivotal axis of said beam, and said reference means;

an arm having its first end pivotally attached to said body such that the plane of motion of the second end of said arm is substantially perpendicular to the strand-engaging surface of said first tang and the strand-engaging surface near the pivotal axis of said beam;

a spring bias means attached to said body and said arm to bias the positioning of said arm with respect to said body; and

a calibrating scale means on at least one side of said body to establish the relative position between said body and the unsupported end of said cantilevered spring, when the unsupported end is deflected.

3. An apparatus to determine a tensional force being carried by a flexible strand, which comprises:

a body;

at least a first and second strand-engaging tang that protrude outwardly and away from said body, and said first and second tang each having a strand-engaging surface;

an arm having its first end pivotally attached to said body such that the plane of motion of the second end of said arm is substantially perpendicular to the strand-engaging surface of said first and second tang;

a spring bias means attached to said body and said arm to bias the positioning of said arm with respect to said body;

a calibrating scale means on at least one side of said body to establish the relative position between said 40 body and said arm; and

a reference means positioned on said body to establish a predetermined angular relationship between the strand-engaging surface of said first strand-engaging tang, the strand-engaging surface of said second strand-engaging tang, and said reference means, said reference means coacting with a surface of the strand to indicate when the segment of strand between said tangs has been deflected a predetermined amount corresponding to said predetermined angular relationship.

4. An apparatus to determine a tensional force being carried by a flexible strand, which comprises:

a body;

a first strand-engaging tang that protrudes outwardly and away from said body and said tang having a strand-engaging surface;

a beam pivotally attached to said body, said beam having a strand-engaging surface near its first end References Cited UNITED STATES PATENTS d aid beam having a strand-engaging surface near 2428379 10/1947 Naumann 73144 2,872,808 2/1959 Ney et a1. 73-144 the pivotal ax1s of said beam,

2,987,913 6/1961 Whltehead, Jr. 73-141 a biasing means between said body and said beam to 3,203,235 8/1965 Stem 73-144 bias the strand-engaglng surface near the first end 3 217 533 11/1965 Able of said beam toward the strand-engaging surface of said first strand-engaging tang; FOREIGN PATENTS a reference means on the second end of said beam to 89,060 10/1896 Ge any establish a predetermined angular relationship between the strand-engaging surface near the first end CHARLES RUEHL, Primary Examiner 

